In a conventional arch type strapping machine, a strapping band is fed to a band guide in an arch member to wind the band around an article to be strapped, and the strapping band is cut and bonded to form a loop, whereby the article is strapped. Such arch type strapping machine is provided with a sealing mechanism for the strapping band. The sealing mechanism comprises a first gripper (hereinbelow, referred to as a right gripper) for fixing a top end of the strapping band fed into the band guide, a second gripper (hereinbelow, referred to as a left gripper) for fixing a rear portion of the strapping band after the band has been pulled back to be tightened and a compression head for compressing and bonding (in many cases, melt-bonding) the top end and the rear portion of the strapping band and cutting the rear portion of the band. The right gripper, the left gripper and the compression head are operated by driving cams attached to a shaft for sealing which is rotated and driven by a motor for sealing.
In the conventional arch type strapping machine, a step for pulling back the strapping band at a high speed and a step for tightening the band at a high torque intervene between the operation of the right gripper and the operation of the left gripper. Accordingly, in the operation of the above-mentioned sealing mechanism, it is necessary that the rotation of the shaft for sealing is once stopped after the right gripper has been operated, and the shaft for sealing is again rotated to cause the operations of the left gripper and the compression head after the step for pulling back the band at a high speed and the step for tightening the band at a high torque have been finished. Accordingly, it is difficult to rotate the shaft for sealing at a high speed whereby a demand of shortening the cycle of strapping can not be satisfied sufficiently. Further, the service life of the sealing mechanism is short because the number of times of temporary stop of the driving system in the sealing mechanism is many.
Further, in a conventional arch type strapping machine, an article is strapped by performing a band feeding step for feeding a strapping band into a band guide in an arch member, a first tightening step for winding the strapping band around an article to be strapped by returning quickly the band fed into the band guide, a second tightening step for tightening strongly the strapping band wound around the article by returning the band, and a step for bonding (in many cases, melt-bonding) a rear portion and a top end of the band wound around the article to be strapped and cutting the band. The band feeding step and the first and second tightening steps are carried out by a driving mechanism comprising a plurality of rollers for running and tightening the strapping band.
Such driving mechanism for the strapping band makes the size of the arch type strapping machine large because a plurality of driving rollers are used, e.g., a driving roller for performing the band feeding step as well as the first tightening step and a driving roller for performing the second tightening step being provided separately. Accordingly, this is contrary to a demand of reducing the size of the arch type strapping machine.
Further, in a conventional arch type strapping machine, an article is strapped with a strapping band in such a manner that the strapping band is fed into a groove formed in a band guide having a channel-like shape in cross section, an open side of which is pushed to an inner surface of the arch member; the strapping band fed into the band guide is wound around the article to be strapped by returning the band at a high speed; the strapping band wound around the article is tightened by pulling it back, and the cutting of a rear portion of the band and bonding (melt-bonding) of the rear portion to an top end of the band is conducted. The returning of the strapping band at a high speed is conducted immediately after the state that the strapping band leaves entirely or partly from the band guide, such state being obtainable by opening forcibly the band guide in a direction departing from the inner surface of the arch member with which the band guide is brought into contact.
The width or the height (in particular, the height) of the groove of the band guide is formed to be relatively small so that the strapping band can be certainly passed without causing the bending of a top end of the band. In the operation for opening the band guide, there is a possibility that the strapping band follows the movement of the band guide due to a frictional force between an inner surface of the groove and the strapping band, and the band remains in the groove. If the strapping band is tightened at a high speed in the state that the strapping band remains in the groove, an unusual deformation is caused instantaneously in the band guide at the time of leaving the strapping band, whereby the band guide is damaged.
Further, in a conventional arch type strapping machine, the strapping band is rewound from a band roll fitted to a band reel which is attached to an outer side of the arch type strapping machine, to be stored temporarily in a band accommodation chamber in the strapping machine. Then, the strapping band in the band accommodation chamber is successively fed into the band guide.
In many cases, the band reel comprises a supporting shaft having an end supported by the main body of the strapping machine, a reed portion attached to the supporting shaft so that at least a part (in many cases, a rear side plate) is removable from the supporting shaft, the reel portion being adapted to mount the band roll for the strapping band, and a nob attached to a rear end of the supporting shaft to fix the reel portion. When a used band roll mounted on the band reel is replaced by a new one, the nob and, for instance, the rear side plate are removed from the supporting shaft; the core member of the used band roll is removed from the reel portion; a new band roll is attached to a reel portion, and then, the rear side plate and the nob are fixed again to the supporting shaft.
In many cases, the structure for fitting the nob to the supporting shaft comprises a male screw formed in a rear end (the free end) of the supporting shaft and a female screw formed in the nob so that the nob can be fitted to the supporting shaft by rotating it several times of turn. Accordingly, in the replacement of the band roll, it is necessary to turn back the tightly fastened nob, and the nob is tightly fastened by rotating after new band roll is mounted. Accordingly, the working for replacing the band roll is troublesome.
It is an object of the present invention to provide an arch type strapping machine having a sealing mechanism for cutting and bonding a strapping band fed into the band guide of the strapping machine, which is capable of achieving the speed-up of strapping operations and having a long service life.
Further, it is an object of the present invention to provide an arch type strapping machine having a strapping band driving mechanism for feeding the strapping band into the band guide and pulling back the band, which is suitable for reducing the size of the strapping machine.
Further, it is an object of the present invention to provide an arch type strapping machine having a band reel adapted to mount a band roll on which the strapping band fed into the band guide is wound, which permits the fitting and the removal of a nob easily.
Further, it is an object of the present invention to provide an arch type strapping machine having a band driving-out device which can provide a state that the strapping band leaves certainly from a groove for receiving the band at the time of opening the band guide without losing a smooth opening operation of the band guide.
In accordance with an aspect of the present invention, there is provided an arch type strapping machine having a sealing mechanism which comprises a right gripper for fixing a top end of a strapping band fed into a band guide of the arch type strapping machine; a left gripper for fixing a rear portion of the strapping band after the strapping band has been wound around an article to be strapped and tightened; a compression head for compressing and bonding the top end and the rear portion of the strapping band and cutting the rear portion of the band, and a driving means for operating the right gripper, the left gripper and the compression head, said arch type strapping machine being characterized in that the driving means of the sealing mechanism comprises a first driving section for operating the right gripper and a second driving section for operating the left gripper and the compression head, wherein the second driving section comprises a motor for sealing, a shaft for sealing rotated by the motor, a cam for fixing attached to the shaft for sealing to operate the left gripper, and a cam for bonding to operate the compression head.
In accordance with another aspect of the present invention, there is provided an arch type strapping machine having a strapping band driving mechanism which performs a band feeding step for feeding a strapping band into a band guide of the arch type strapping machine, a first tightening step for winding the strapping band around an article to be strapped by returning quickly the strapping band fed into the band guide and a second tightening step for tightening strongly the strapping band around the article by pulling back the strapping band, the arch type strapping machine being characterized in that the strapping band driving mechanism comprises a d.c. motor capable of rotating in a positive direction of feeding and in a reverse direction of returning; a band driving roller attached to an end of an output shaft for band-running of the d.c. motor and a motor for driving a shaft for sealing, connected to the output shaft via an electromagnetic clutch which is attached to the other end of the output shaft of the d.c. motor, wherein the band feeding step is performed by the rotation of the band driving roller caused by the rotation in a direction of feeding of the d.c. motor; the first tightening step is performed by the rotation of the band driving roller which is caused by the rotation in a direction of returning of the d.c. motor, and the second tightening step is performed by the rotation of the band driving roller which is caused by an output of rotation from the motor for driving the shaft for sealing via the electromagnetic clutch.
The output of rotation from the motor fro driving the shaft for sealing, which is transmitted by connecting the electromagnetic clutch is in many cases, an output of a low speed/high torque rotation.
In accordance with another aspect of the present invention, there is provided an arch type strapping machine having a band driving-out device adapted to discharge a strapping band from a band guide when the band guide disposed in an arch member of the arch type strapping machine is opened whereby the strapping band is prevented from remaining in a band groove, the arch type strapping machine being characterized in that the band driving-out device comprises a push pin inserted movably in a through hole formed in a rear portion of the band guide, a pin stopper disposed to oppose a head portion of the push pin, and a spring member disposed between the rear portion of the band guide and the head portion of the push pin so as to push the head portion of the push pin to bring it into contact with the pin stopper.
In accordance with another aspect of the present invention, there is provided an arch type strapping machine having a band reel for a strapping band, the arch type strapping machine being characterized in that the band reel for a strapping band comprises a supporting shaft having an end supported by the main body of the strapping machine, a reel portion attached to the supporting shaft, which is adapted to mount a band roll on which a strapping band fed to a band guide in an arch member of the arch type strapping machine is wound, and a nob attached to a rear end of the supporting shaft to fix the reel portion, wherein the nob has a cylindrical portion fitted to an outer periphery of a rear end of the supporting shaft; the cylindrical portion is provided with a guide groove extending spirally from its front side to its rear side; a recess is formed in the innermost portion of the guide groove, and a pin capable of passing relatively the guide groove to fit to the recess is provided in a rear end portion of the supporting shaft.
The supporting shaft may be such one supported rotatably by the main body of the strapping machine. In this specification, the side of the supporting shaft supported by the main body of the strapping machine is referred to as a front side. The rear end of the supporting shaft is free. The nob for fixing the reel portion may be a cap. The recess may be a groove.